Apparatus for producing dendrites

Claim 1

A TOP HAT COVER FOR AN APPARATUS COMPRISING A CRUCILE FROM WHICH SEMICONDUCTOR MATERIAL IN DENDRITIC CRYSTALLINE FORM IS PRODUCED BY THE CONTINUOUS WITHDRAWAL THEREOF FROM A SUBSTANTIALLY CIRCULAR SUPERCOOLED MELT OF THE MATERIAL, THE COVER COMPRISING (1) A FIRST BRIM-LIKE REFLECTING MEANS COMPRISING AT LEAST TWO SUBSTANTIALLY FLAT METAL WASHER-LIKE MEMBERS SLIGHTLY SPACED APART, THE LOWER FIRST EXTENDING FROM THE OUTER PERIPHERY OF THE CRUCIBLE RADIALLY INWARDLY SO AS TO COVER ABOUT THE OUTER 13 TO 19% OF THE MELT DIAMETER WHILE THE SECOND UPPER WASHER MEMBER HAS A SLIGHTLY SMALLER INSIDE APERTURE COOPERATING TO REFLECT HEAT DOWNWARD INTO THEMELT PRIMARILY INTO THE OUTER 25 TO 35% OF THE MELT DIAMETER, THE REFLECTIVE MEMBERS BEING OF A METAL BEING A REFLECTIVITY OF AT LEAST 80%, (2) A HOLLOW CIRCULAR THERMALLY INSULATING CYLINDER EXTENDING UPWARDLY FROM THE INSIDE OF THE SAID SECOND UPPER WASHER MEMBER, THE INSULATING MEMBERHAVING AN INSIDE DIAMETER OF APPROXIMATELY 2/3 THE MELT DIAMETER AND EXTENDING UPWARDLY FROM THE FIRST REFLECTING MEANS BY AN AMOUNT OF ABOUT HALF THE MELT DIAMETER, AND (3) A SECOND REFLECTING MEANS COMPRISING AT LEAST ONE SUBSTANTIALLY FLAT WASHER-LIKE METAL MEMBER OF A REFLECTIVITY OF AT LEAST 80% AND HAVING AN APERTURE OF A DIAMETER EQUAL TO ABOUT THE RADIUS OF THE MELT AND BEING DISPOSED WITHIN SAID INSULATING CYLINDER SO AS TO LIE IN A PLANE SUBSTANTIALLY PARALLEL TO THE SURFACE OF THE MELT AND MEANS FOR POSITIONING THE SECOND REFLECTING MEANS VERTICALLY ALONG THE LENGTH OF THE INSULATING CYLINDER SUCH THAT (A) HEAT IS REFLECTED THEREBY INTO THE OUTER PORTIONS OF THE MELT AND (B) COOPERATING WITH THE SAID INSULATING CYLINDER TO CONTROL THE THERMAL GRADIENT ALONG THE DENDRITE AS IT IS WITHDRAWN FROM THE MELT.